Based on the published co-infection and the cellular receptor study, we proposed that C4a and C4b viruses are intertypic recombination viruses between EV71 and other HEV-A strains derived from CVA16 or CVA14, not CVA4, since CVA4 infected cells via the different cellular receptor pathway and associated mainly with different clinical outcome, herpangina [33]. Here, C4A is linked to coinfection.